Self balancing centrifugal testing device



June 23, 1964 s. s. LINN 3,138,021

SELF BALANCING CENTRIFUGAL TESTING DEVICE Filed Feb. 6, 1961 may INVENTOR,

@0221 9 QCQQM United States Patent 3,138,021 SELF BALANCING CENTRIFUGAL TESTING DEVICE Sidney S. Linn, Garden City, N.Y., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Army Filed Feb. 6, 1961, Ser. No. 87,512 1 Claim. (Cl. 73-167) This invention relates to a dynamically self-balancing centrifugal device for testing centrifugally armed fuzes of the type generally disclosed in US. Patents 2,014,393 and 2,818,812, and is more particularly directed to a discshaped fuze holder suspended from a high speed motor by means of a flexible shaft and rotated thereby.

As is well known in the fuzing art, the fuze of a spin stabilized projectile is in many instances of the type armed by centrifugal force as it rotates about its axis of flight.

In order to determine with any degree of certainty and accuracy whether or not such fuze will properly arm its projectile when fired, it has been found useful to simulate free-flight rotation in production line testing of these fuzes. In any such testing, however, it is important that the fuze be free to rotate about an axis passing through its center of mass, and not be constrained to rotate about its geometric axis, though ideally these two axes should be coincidental, since such center of mass rotation most closely approaches free-flight conditions. Therefore, merely securing the fuze in a rotating chuck having a fixed axis of rotation, as in the prior art devices, will not simulate the desired flight conditions. Thus, it is apparent that the prior art devices have shortcomings which materially affect the quality control aspects of fuze testing.

Accordingly, an object of this invention is to overcome these prior art deficiencies by providing a testing device which will rotate a fuze at high speed about the longitudinal axis passing through the center of mass thereof.

Another object is to provide a device for testing centrifugally operated components which device is simple and inexpensive to construct and operate.

A further object is to provide a centrifugal testing device having a snubbing or bumper means around and spaced from the spinning periphery thereof.

These and other objects will be apparent from the following detailed description and accompanying drawings in which:

FIGURE 1 illustrates a sectional elevation of the testing device;

FIGURE 2 illustrates a plan view sighted on line 22 of FIGURE 1; and

FIGURE 3 illustrates a section taken on line 33 of FIGURE 1.

Referring now to the drawing and more particularly to FIGURE 1, there is illustrated therein a high speed motor supported on a table or frame 14. The shaft of motor 10 terminates in a hollow socket receiving one end 17 of flexible shaft 18. A collet 16 is fitted about socket 12 and the parts are held together by means of a pin 16. The other end 19 of shaft 18 is fitted in a chuck 23 received in a disc 20 there being a pin 19 securing shaft 18, chuck 23 and disc 20 together. Disc 20 has an annular grooved recess 22 on the under portion thereof forming an inner peripheral track or raceway for a plurality of spherical balls 24. As is apparent from FIGURE 1, disc 20 is adapted for rotation in a horizontal plane about its vertical axis AA. Disc 20 further has a threaded recess 3,138,021 Patented June 23, 1964 26 on its underside along axis AA, said recess being adopted for threadedly receiving a component to be centrifugally tested such as fuze 25. Surrounding disc 20 about its outer periphery and spaced apart therefrom is a series of resilient bumper elements 27, each of which consists of a bottom ring 29, a resilient roller 30, a roller bearing support 30 and an assembling bolt 28 which extends through the elements 27 and the mounting support 31. It will be noted that the rollers 30 overhang the rings 29 but still remain out of contact with disc 20. Support 31 has an opening 32 therein which is concentric with disc 20 for accessibility to the underside of disc 20.

In operation the device functions as follows: a test component, such as fuze 25, is threadedly secured within recess 26 of disc 20. Motor 10 is energized and by means of flexible shaft 18, will rotate disc 20 and fuze 25 at approximately 120,000 r.p.m.

Because of the self balancing feature of applicants device due to the annular track and ball arrangement, the spin axis of mass of the fuze and disc combination will tend to become coincident with the systems geometric axis thereby simulating free-flight conditions. The selfbalancing characteristics of applicants device operate on the principle of dynamics that for any speed of rotation above the first critical speed, the system comprising the disc 20 mounted on the flexible shaft 18 will tend to rotate about an axis passing through its center of mass, whereas below this critical speed the disc 20 will tend to rotate about its geometric axis. Therefore, at speeds above the critical speed, i.e. when disc 20 is rotating about its center of mass, the lighter side of the disc is moved to a position further away from the mass axis of rotation than the heavier side. The steel balls 24 are permitted to roll freely around annular groove 22 so that above the critical speed centrifugal force will move balls 24 outwardly toward the lighter side of the spinning disc thereby tending to bring the dynamic axis of rotation into alignment with geometric axis AA.

Thus, it can be seen that by employing the herein disclosed device, it is possible to determine whether or not a fuze, such as that generally described in US. Patents 2,014,393 and 2,818,812, will properly function during its free flight thereby precluding potential dud projectiles due to malfunctioning of its fuze.

Various modifications are contemplated and may obviously by resorted to by those skilled in the art without departing from the spirit and scope of the invention, as here inafter defined by the appended claim, as only a preferred embodiment thereof has been disclosed.

What is claimed and desired to be secured by Letters Patent of the United States is:

A centrifugally operated self-balancing fuze testing device including in combination, a first support; a power means carried by said first support; a flexible shaft connected at one end to said power means, said shaft driven by and depending vertically from said power means; a discshaped holder fixed to the other end of said shaft, said disc-shaped holder comprising a circular member having an annular, coaxial, internally threaded recess in its bottom surface for threadably engaging a fuze therein, said recess having an annular groove around its greater periphery, a plurality of spheres located within said groove and free to travel around said groove during rotation of said disc; a second support disposed below said holder, said second support having a circular opening coaxial with said shaft and said holder and a plurality of resilient bumper elements supported in peripheral arrangement on said second support and in spaced relation to the outer peripheral surface of said holder, each said bumper element comprising a bearing assembly mounted on said second support and overhanging said bearing assembly whereby said bumper elements serve to limit excessive oscillatory motion of the disc-shaped holder which would occur during critical ranges of rotational speed of the disc-shaped holder if the fuze were in an unbalanced condition.

References Cited in the file of this patent UNITED STATES PATENTS Jahn Aug. 8, 1916 Persson June 15, 1943 Gurin Nov. 20, 1956 Gooch June 18, 1960 Kopczynski Mar. 27, 1962 Hack Feb. 5, 1963 

